Electrolytic capacitor and method of preparing it

ABSTRACT

The present invention is an electrolytic capacitor comprising a titanium-deposited aluminum foil used as the cathode. An aluminum foil is subjected to vacuum deposition of titanium with a deposition angle, thereby obtaining an electrolytic capacitor having a larger electrostatic capacitance than the conventional.

TECHNICAL FIELD

The present invention relates to an electrolytic capacitor usingaluminum as electrode foil, utilized in various electronic equipments,and a method of preparing it.

BACKGROUND ART

Electrolytic capacitors of this type have been hitherto constituted ofan anode foil on which an anodized dielectric film is formed, comprisinga high purity aluminum foil electrolytically etched to expand itseffective areas and then subjected to formation treatment, and a cathodefoil employing an aluminum foil electrolytically etched to expand itseffective areas, which foils are wound interposing a separator followedby impregnation with a driving electrolyte (hereinafter "paste").

Such electrolytic capacitors used in commonly available electronicequipments are strongly demanded to be made more compact and thinnerwith the trend of making various electronic equipments more compact andthinner.

Incidentally, the capacitance C of electrolytic capacitors is thecomposite capacitance of the anode capacitance C.sub.⊕ with the cathodecapacitance C.sub.⊖, and represented by the following formula: ##EQU1##Accordingly, it has been attempted to increase not only theelectrostatic capacitance of the anode foil but also that of the cathodefoil, but an excessive etching causes surface dissolution of aluminumfoils to proceed and prevents the electrostatic capacitance fromincreasing, and also the etching resulting from non-uniform dissolutionbrings about an extreme lowering of foil strength, so that, since thefoils are made to have smaller widths to make them compact, it has beenfurther impossible to wind foils in a high speed, thus leaving a limitin increasing the electrostatic capacitance of cathode foils by usingelectrolytic etching techniques.

As a means for improving it, it is known to form a titanium-depositedfilm on the roughened surfaces of aluminum foils (for example, JapaneseUnexamined Patent Publications No. 180420/1986 and No. 214420/1986).

The cathode foils obtained by such a titanium vacuum deposition processcan have a greater surface area and a more increased electrostaticcapacitance than those obtained by the electrolytic etching process, buthave had the disadvantages that they have too dense a structure to beimpregnated with the paste with ease and therefore the electrostaticcapacitance can be effectively exhibited with difficulty as capacitors.

They also have had the disadvantage that a lowering of capacitance iscaused when vacuum deposition is continuously carried out.

DISCLOSURE OF THE INVENTION

The present invention aims at eliminating these disadvantagesconventionally involved, and an object thereof is to provide anelectrolytic capacitor that employs a high-capacitance cathode foilobtainable as a result of studying titanium vacuum deposition.

Namely, the present invention employs as the cathode foil an aluminumfoil obtained by vacuum deposition of titanium with a deposition angleon the deposition surface, said vacuum deposition being carried out inan argon gas atmosphere kept within the range of from 1.0×10⁻⁵ to1.0×10⁻⁴ Torr, while controlling to from 50° to 200° C. the temperatureon the deposition surface of an aluminum foil substrate made to have anenlarged surface area.

Such titanium vacuum deposition results in the formation of a titaniumfilm with a rough column-like structure comprising columns independentfrom each other. Employment of such an electrode enables the titaniumcolumn-like structure film to be impregnated with the paste through itsdetails, resulting in an increase in the effective surface area, animprovement in the electrostatic capacitance, and an improvement in theelectrostatic capacitance of electrolytic capacitors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-a and 1-b are cross sections of aluminum foils;

FIG. 2 is a schematic view to illustrate a vacuum deposition method bywhich the deposition angle θ is given;

FIGS. 3 and 4 are views to show the relationship between the vacuumdeposition angle and capacitance;

FIG. 5 is a view to show the relationship between the depositiontemperature and capacitance;

FIG. 6 is a schematic view of a vacuum deposition apparatus for use inmass-production; and

FIG. 7 is a view to show the relationship between the depositiondistance and capacitance.

BEST MODES FOR WORKING THE INVENTION

Examples of the present invention will be described below.

The present inventors made various studies on instances in which vacuumdeposition is carried out on aluminum foil substrate. The items of thesestudies included the deposition angle, temperature, atmosphere, etc.,and studies were also made on the characteristics of electrolyticcapacitors by using as the cathode the aluminum foils subjected tovacuum deposition under various conditions.

(Example 1)

In the first place, studies were made on the deposition angle.

Enlarged model cross sections of titanium vacuum deposited filmstructures are shown in FIG. 1. FIG. 1(a) shows a structure of a filmformed by conventional etching, and FIG. 1(b) is a model view of atitanium vacuum deposited film formed with the deposition angleaccording to the present invention. As a result of various studies somade that rough titanium vacuum deposited films can be obtained, givingthe deposition angle (θ) gives 1/cos θ per unit area with increase inthe angle θ, resulting in rough vacuum deposition, so that the film canhave the column-like structure as in FIG. 1(b), comprising columnsindependent from each other.

In industrial actual manufacture, giving the deposition angle θ resultsin a poor deposition efficiency, and also requires a very large-scalevacuum deposition apparatus. Taking account of these, an idea wasconceived that the vacuum deposition may be so carried out that nucleimay be formed on an aluminum foil substrate 1 at the initial stage oftitanium vacuum deposition to cause a titanium film 2 with a roughcolumn-like structure to grow. Further studies were made based on suchan idea, to find that, as illustrated in FIG. 2, a revolving roll (whichmay be a square roll, but commonly a round roll) 3 may be used in orderto give the deposition angle θ and yet carry out mass production. InFIG. 2, the numeral 4 denotes aluminum foil; 5, titanium; and 6, a roll.

With an angle given in this way, nuclei with a rough column-likestructure may be deposited and thereafter the film thickness may be madeto continuously grow at the part where a deposited film is formed with agood deposition efficiency and with a small deposition angle, whereby itbecomes possible to continuously and efficiently produce titanium vacuumdeposited films having rough column-like structures.

Specific examples of the present invention will be described below.

First, to evidence the effect of the deposition angle θ, the depositionangle was fixed as shown in FIG. 3, and the relationship between thedeposition angle and capacitance, particularly when deposition wascarried out to give a film thickness of 1.0 μm, provided that the filmthickness smaller than it was calculated as a thickness of 1.0 μm, isshown in Table 1 and FIG. 4. The capacitance was measured using acapacitance inspection solution (composed of 80 g of ammonium borate and1,000 ml of water, and having a specific resistance of 100±10 Ω.cm (30°C.)) and a paste (composed of 10 g of ammonium adipate, 80 g of ethyleneglycol and 10 g of water, as well as small amounts of additives, andhaving a specific resistance of 150±5 Ω.cm (30° C.)).

As electrode foil samples for the measurement, two sheets of sampleswith a dimension of 2.0 cm×1.0 cm were set opposing to carry out themeasurement respectively in the above inspection solution and paste at0.5 Vrms, 120 Hz and a direct bias of 0 V, and the measurements werecalculated in terms of a unit area of 1.0 cm².

As conditions for preparing the samples, the vacuum deposition wascarried out in an argon gas atmosphere at a vacuum degree of 2×10⁻⁵ Torrin a vacuum apparatus, using electron beams as an energy source, wheretitanium was deposited with a film thickness of 1.0 μm, or the filmthickness was calculated as 1.0 μm, to obtain the results as shown inTable 1 and FIG. 4. The unit is expressed by μF/cm².

However, as will be seen from FIG. 3, because of the angles given underthe same conditions, the distance from the deposition source to thealuminum foil substrate differs, so that the deposition efficiency (filmthickness) is lowered in inverse proportion to the second power of thedistance, which is therefore calculated in terms of film thickness andshown in Table 1.

                  TABLE 1                                                         ______________________________________                                        Deposition                                                                    angle θ                                                                           0°                                                                             20°                                                                            40°                                                                           50°                                                                         65°                              ______________________________________                                        Inspection                                                                              108     151     310    818  1,350                                   solution                                                                      Paste     63      82      128    611  1,215                                   Capacitance                                                                              58%     54%      42%    75%                                                                                90%                                   ratio                                                                         (Paste/Inspect-                                                               ion solution)                                                                 ______________________________________                                    

As will be seen from this Table 1 or FIG. 4, the capacitance becomeshigher as the deposition angle θ becomes greater in θ₂ than θ₁. Also, asmaller deposition angle θ gives a denser column-like structure, so thatthe column-like structure can be impregnated through its inside with theinspection solution with difficulty, and the paste, which has a largermolecule and with which the column-like structure can be impregnatedwith difficulty, may be more greatly influenced. On the other hand, withincrease in the deposition angle θ, a rougher column-like structureresults, so that it can be sufficiently impregnated through its insidewith the inspection solution or paste, resulting in great exhibition ofthe capacitance. In particular, a large capacitance was found to havebecome obtainable using the paste actually used with which thecapacitance has been hitherto exhibited with difficulty, and thus theproducts obtained can be used as large capacitance cathode foils for usein capacitors.

Next, an example will be described below in which trial production wascarried out giving the deposition angle and under continuous foiltraveling, using the above apparatus as shown in FIG. 2, which takesaccount of industrial mass production. Foils were produced in an argongas atmosphere and at a vacuum degree of 5×10⁻⁴ Torr as vacuumdeposition conditions, using electron beams as an energy source at anoutput of 6 kW, and at a foil travel speed of 1.0 m/min with atitanium-deposited film thickness of 1.0 μm, and the products weresubjected to the measurement in the inspection solution previouslydescribed and also in the paste previously described. Results obtainedare shown in Table 2. As comparative products, samples were used whichwere prepared under the same vacuum conditions, fixing the depositionangle to 0°, and according to electron beam vacuum deposition with atitanium film thickness of 1.0 μm. Namely, these are in accordance withconventional titanium vacuum deposition conditions.

                  TABLE 2                                                         ______________________________________                                                      Products of                                                                            Comparative                                                          the invention                                                                          products                                               ______________________________________                                        Inspection solution                                                                           1,480      800                                                Paste           1,203      300                                                ______________________________________                                    

Thus, an increase in the capacitance was achieved by the factor of asgreat as about 4 times that of the conventional foil, in the paste whichis used in the actual use as electrolytic capacitors.

Also, capacitors were prepared using titanium-deposited aluminum foilswith the deposition angle according to the present invention (foilsproduced under the same conditions as the above) and comparative foils(the above titanium-deposited foils with a deposition angle of 0°),which were respectively used as cathode foils. Results are shown inTable 3.

The capacitors had an external size of 6.3 mmφ×5 mm length, and wereconstructed by using aluminum foils as anode foils, having a foilthickness of 90 μm and an electrostatic capacitance of 3,000 μF/10 cm²for use in 2 W.V., and impregnating the foils with the above paste.

The electrolytic capacitors had the same construction as theconstruction of the conventional products, and the titanium-depositedfoils prepared under conditions according to the present invention wereused as the cathode.

                  TABLE 3                                                         ______________________________________                                        Sort of capacitor:                                                                    Capacitor of  Conventional                                                    the invention capacitor                                               ______________________________________                                        Cathode   Titanium-deposited                                                                            Titanium-deposited                                            foil with deposition                                                                          foil with 0°                                           angle           deposition angle                                    Capacitance                                                                             480 μF       293 μF                                           ______________________________________                                    

Thus, the capacitance has increased by 64% as compared with thecapacitor in which the conventional titanium-deposited foil is used.

(Example 2)

Next, studies were made on the deposition temperature. The temperaturesof the aluminum foil 4 were controlled to 25° to 400° C. and titaniumwas vacuum deposited, and capacitance values in a driving electrolyte,thus obtained, are shown in FIG. 5. As is evident from this FIG. 5, thecapacitance is seen to have been improved when the temperatures of thealuminum foil 4 are in the range of from 50° to 200° C.

Thus, the titanium-deposited film with the rough structure, suited toelectrode foils for use in electrolytic capacitors, is seen to have beenformed in the range of from 50° to 200° C.

Cathode foils obtained in the above way were built in aluminumelectrolytic capacitors, the results from which are shown in Table 4.

                  TABLE 4                                                         ______________________________________                                        (Rated voltage: 4V; case size: θ8 × 7)                                                    Electrostatic                                         Temperature Electrostatic                                                                             capacitance of                                        of the deposit                                                                            capacitance of                                                                            aluminum electro-                                     surface     electrode foil                                                                            lytic capacitor                                       (°C.)                                                                              (μF/cm.sup.2)                                                                          (μF)                                               ______________________________________                                         25         1,000       424                                                   120         1,370       560                                                   250         1,000       406                                                   ______________________________________                                    

As shown in Table 4, in the typical example of the present invention,where the foil having been subjected to vacuum deposition at 120° wasbuilt in the electrolytic capacitor as the cathode foil, theelectrostatic capacitance thereof is greatly enhanced.

Also, with respect to the decrease in capacitance owing to thecontinuous vacuum deposition, the present invention takes note of thefact that the heat from the vacuum deposition source raises the foiltemperature in carrying out the vacuum deposition for titanium-depositedfoils, and hence a film which is dense and has a small surface area isformed, resulting in a lowering of the capacitance. These phenomena canbe observed using a high-magnification electron microscope. To give thecolumn-like structure, it is required for the temperature to be set tofrom 50° to 200° C.

In carrying out the continuous vacuum deposition, however, the aluminumfoil substrate is gradually heated by the heat from the vacuumdeposition source, until it is heated to a high temperature of 200° C.or more. For this reason, it was noted to cool this heated substrate,and thus, in particular, the roll coming into close contact therewith incarrying out the vacuum deposition is internally cooled using water or arefrigerant, thereby preventing the temperature of the aluminum foilsubstrate from being raised, so that there can be taken the roughcolumn-like structure with a large surface area.

The refrigerent may take the form of gas or liquid, but the gas is notsuitable because of its small thermal conductivity and thermal capacity,and liquids, water or halogen solvents, are preferred, and there can beapplied a circulation system, a discharging system, etc. in variety.These can be freely selected taking account of cost, efficiency, etc.

To increase the cooling efficiency, a mere bath roll may also be used asa cooling roll to increase the heat dissipation effect of the aluminumfoil substrate.

A specific vacuum deposition apparatus is schematically illustrated inFIG. 6.

The aluminum foil 4 is unrolled in the inside of a vacuum chamber bymeans of a let-off roll 16, and titanium 5 heated in a crucible 15 isdeposited on each surface using a vacuum deposition roll. The resultingfoil is let to travel toward a roll-up roll 17 and rolled up there. Inthe course of the traveling path, the aluminum foil 4 passes on severalrolls 6, so that its travel direction is changed. A shutter 18 is closeduntil the depositing titanium 5 become stable by preliminary dissolutionor the like so that vacuum deposition of titanium may be prevented.

It is a characteristic feature that the vacuum deposition is carried outwhile cooling this vacuum deposition roll 3 or optionally the rolls 6.

An example of the present invention will be described below usingspecific data. In the example, the vacuum deposition roll 3 in FIG. 6was made to comprise a roll of a water-cooling type, and the vacuumdeposition was carried out under water cooling.

As vacuum deposition conditions, the vacuum deposition was carried outin an argon gas atmosphere at a vacuum degree of 2×10⁻⁴ Torr and at avacuum deposition foil travel speed of 2 m/min, using a vacuumdeposition source energy with an EB (electron beam) output of 8 kW. Twosheets of samples with a dimension of 2.0 cm×1.0 cm were set opposing tocarry out the measurement of the foil capacitance in a capacitanceinspection solution.

Composition of the capacitance inspection solution:

    ______________________________________                                        Ammonium borate     80 g                                                      Water             1,000 g                                                     ______________________________________                                    

Specific resistance: 100±10 Ω.cm (30° C.)

The vacuum deposition was continuously carried out over a length of 100m, and sampling was carried out at intervals of 10 m to carry out themeasurement. Results obtained are shown in Table 5.

                  TABLE 5                                                         ______________________________________                                                The begin-                                                                    ning of   10 m                                                        Roll    deposition,                                                                             (roll    20 to 100 m                                        used    l m       temp.)   (roll temp.)                                                                            Remarks                                  ______________________________________                                        Conven- 1,205       504    275 to 481                                                                              X                                        tional  (25° C.)                                                                         (58° C.)                                                                        (67 to 213° C.)                             roll                                                                          Cooling 1,310     1,283    1,165 to 1,342                                                                          Y                                        roll    (22° C.)                                                                         (23° C.)                                                                        (22 to 23° C.)                              ______________________________________                                         *In the parentheses, roll temperatures are given, which are values            measured with a thermocouple in the roll.                                     X: Capacitance greatly changed, resulting in a lowering of capacitance.       Y: A large capacitance with less scattering of capacitance.              

As shown in Table 5, the foil on which the vacuum deposition was carriedout using the cooling roll keeps a large capacitance level with lessscattering of capacitance, and thus the cooling roll is seen to bringabout a very great effect.

FIG. 7 shows capacitance values measured at intervals of 10 m.

Also, the capacitor of the present invention, in which the aluminumfoil, deposited with titanium using the cooling roll, was used as thecathode was compared with the capacitor in which the cathode formed bythe conventional electrolytic etching process was used, and thecharacteristics thereof are shown in Table 6. In both cases, the anodecomprises an aluminum foil formed under the same conditions.

The capacitance of the cathode is 1,210 μF/cm² in respect of thetitanium-deposited cathodes, and 308 μF/cm² in respect of the abovecomparative cathode. The products had a dimension of 8 mmφ×7 mm length,and a titanium film thickness of about 1 μm. The capacitance measurementsolution is composed of 80 g of ammonium borate and 1,000 ml of water,and has a specific resistance of 100±10 Ω.cm (30° C.). Used as the pastewas the one composed of 10 g of antimon adipate, 80 g of ethylene glycoland 10 g of water, as well as small amounts of additives, and having aspecific resistance of 150±5 Ω.cm (30° C.)).

As electrode foil samples for the measurement, two sheets of sampleswith a dimension of 2.0 cm×1.0 cm were set opposing to carry out themeasurement respectively in the above capacitance measurement solutionand driving electrolyte.

The vacuum degree was first adjusted to 10⁻⁷ Torr or less, and argon gaswas fed to set the respective vacuum degrees. If oxygen gas or nitrogengas is present, reaction may occur to form titanium oxide or titaniumnitride to bring about differences in states, and therefore a highvacuum was once produced and then unreactive inert argon gas was fed toadjust the vacuum degrees. As the inert gas, helium gas or the like maybe satisfactory, but the argon gas, which exists in a large quantity andis readily available with a low cost, was used taking account of thecost.

As shown in Table 6, a low vacuum with a vacuum degree of from 1.0×10⁻⁵to 10×10⁻⁴ Torr results in the rough film structure, making it possibleto obtain a large capacitance. Further, the lower vacuum is given, thelarger capacitance can be obtained. However, a low vacuum of 10⁻³ Torrresults in excessively frequent collisions of argon gas against titaniumvapor to worsen deposition efficiency and also lower the capacitance.Moreover, the low vacuum of 10⁻³ Torr brings about an ion bombardmentphenomenon of argon gas, which causes cut-off of a filament of theenergy-generating source during its use for a short period of time,resulting in a short lifetime, and further enables no continuous usebecause of the condition to readily cause abnormal discharge. Namely,the vacuum deposition of titanium at vacuum degrees of from 1.0×10⁻⁵ to10×10⁻⁴ Torr brings about the film structure that can obtain a largecapacitance, which are conditions under which a good vacuum depositionefficiency, i.e., a good productivity can be achieved.

Table 6 shows the capacitance measured in the capacitance measurementsolution and paste.

                  TABLE 6                                                         ______________________________________                                        (Unit of vacuum degree: Torr; unit                                            of capacitance: μF/cm.sup.2)                                               ______________________________________                                                Vacuum degree:                                                        Torr      8 × 10.sup.-4                                                                    2 × 10.sup.-5                                                                      8 × 10.sup.-5                                                                  2 × 10.sup.-4                      ______________________________________                                        Measurement                                                                             493      1,020      1,131  1,352                                    solution                                                                      μF/cm.sup.2                                                                Paste     87       681        925    1,040                                    μF/cm.sup.2                                                                ______________________________________                                                Vacuum degree:                                                        Torr      5 × 10.sup.-4                                                                    8 × 10.sup.-4                                                                      2 × 10.sup.-3                                                                  5 × 10.sup.-3                      ______________________________________                                        Measurement                                                                             1,393    1,504      1,361  1,001                                    solution                                                                      μF/cm.sup.2                                                                Paste     1,122    1,190      1,135  908                                      μF/cm.sup.2                                                                ______________________________________                                         The foregoing is summarized in Table 7.                                  

                  TABLE 7                                                         ______________________________________                                        Vacuum degree                                                                            Capacitance       Others                                           ______________________________________                                        High vacuum of                                                                           Dense film structure                                               10.sup.-6 Torr                                                                           with a small capacitance.                                          or more                                                                                  Rough film structure                                                                            No abnormal-                                     10.sup.-5 to 10.sup.-4                                                                   with a large capacitance.                                                                       ity in                                           Torr       The lower the vacuum is                                                                         continuous                                                  (10.sup.-4 Torr), the larger                                                                    operability,                                                the capacitance is.                                                                             etc.                                             Low vacuum of                                                                            Rough film structure                                                                            Liable to                                        not more than                                                                            with a large capacitance,                                                                       abnormal                                         10.sup.-3 Torr                                                                           but a lowering of discharge.                                                  deposition efficiency                                                                           Filament is                                                 with a decrease in                                                                              liable to                                                   capacitance.      cut-off.                                                                      (Continuous                                                                   production                                                                    impossible,                                                                   accordingly).                                    ______________________________________                                    

                  TABLE 8                                                         ______________________________________                                                              Cathode foil                                                                             Product                                      Sort of   Cathode foil                                                                              capacitance                                                                              capacitance                                  product   used        (μF/cm.sup.2)                                                                         (μF)                                      ______________________________________                                        Product of                                                                              Titanium-   1,210      1,103                                        the invention                                                                           deposited                                                                     aluminum                                                                      foil                                                                Conventional                                                                            Electolytic   308        441                                        product   etching foil                                                        ______________________________________                                    

As shown in Table 8, it was also possible to obtain a capacitance of 2.5times by only changing the cathode foil under the same conditions.

The capacitance of the cathode formed without use of the cooling rollbecomes smaller under the influence of heat, to have the same level asthe conventional electrolytic etching foil, resulting, moreover, inscattering of the capacitance.

(Example 3)

The present inventors also made studies on vacuum degrees.

In general, the vacuum deposition is carried out at a high vacuum degreeso that adhesion can be enhanced and a dense film can be prepared. Inthe present invention, the vacuum degrees were studied taking note ofconversely making larger the surface area, in other words, preparing arough film, in order to increase the capacitance, and this was madepossible by carrying out vacuum deposition of titanium at a low vacuumdegree. This is based on the mechanism that titanium vapor collidesagainst gaseous molecules between the vacuum deposition source andvacuum deposition substrate (herein the argon gas molecules which are inthe space in which the titanium reaches the vacuum deposition substrateand adheres thereon) to make kinetic energy smaller, thus forming arough film structure.

Using as the cathode the titanium-deposited foil prepared in this way at5×10⁻⁴ Torr which is within the range of vacuum deposition conditions ofthe present invention, an electrolytic capacitor was experimentallyprepared to obtain the results as shown below. A foil subjected to 5 Vformation was used as a cathode foil, and a capacitor comprising acathode foil formed by the conventional etching process and having acapacitance of 300 μF/cm² was used as a comparative capacitor. If theproduct has a dimension of 6.3 mm in diameter and 7 mm in length, theelectrolytic capacitor of the present invention can obtain a capacitanceof 612 μF, but the comparative capacitor can only obtain a capacitanceof 285 μF, which is not more than the half. The values are shown inTable 9.

                  TABLE 9                                                         ______________________________________                                                     Dimension (φ × l )                                                              Capacitance                                          ______________________________________                                        Capacitor of the invention                                                                   6.3 mm × 7 mm                                                                         612 μF                                        Capacitor comprising the                                                                     6.3 mm × 7 mm                                                                         285 μF                                        conventional cathode                                                          ______________________________________                                    

Thus, the electrolytic capacitor of the present invention, which employsas the cathode the aluminum foil vacuum-deposited with titanium in anargon atmosphere at a vacuum degree of from 1.0×10⁻⁵ to 10×10⁻⁴ Torr,can be compact and obtain a large capacitance.

POSSIBILITY OF INDUSTRIAL UTILIZATION

As described in the above, the electrolytic capacitor which employs asthe cathode the titanium-deposited aluminum foil according to thepresent invention, can achieve a great increase in the electrostaticcapacitance, can be made very compact, can be made thinner, can be madeto have a large capacitance, bringing about great advantages in theequipments to be used, and yet can be continuously produced, having agreat effect of mass production when produced, so that it can achieve agreat improvement in the production cost or the like, thus making agreat contribution to industries.

We claim:
 1. A method for producing an electrolytic capacitor whichcomprises, providing a cooling roll on which an aluminum foil substrateis to be deposited with titanium at a deposition angle which allowsformation of rough column-like structures, continuously passing analuminum foil substrate in close contact with said cooling roll whilekeeping the temperature of said aluminum foil substrate in the range offrom 50° to 200° C., subjecting said aluminum foil substrate to vacuumdeposition with titanium on the surface of said cooling roll in anatmosphere of argon gas at a degree of vacuum of from 1.0×10⁻⁵ to1.0×10⁻⁴ Torr, thereby forming a cathode foil, winding said cathode foiltogether with an anode foil with a separator interposed therebetween toform a capacitor unit, and impregnating said capacitor unit with adriving electrolyte.
 2. A method according to claim 1, wherein saiddeposition angle is gradually varied during said deposition of saidtitanium.
 3. A method according to claim 1, wherein said depositionangle at an initial stage of said deposition is 40° or greater.
 4. Amethod of producing an electrolytic capacitor according to claim 3,wherein the temperature of said aluminum foil substrate is maintained inthe range of from 50° to 200° during said vacuum deposition.
 5. A methodof producing an electrolytic capacitor according to claim 3, whereinsaid aluminum foil substrate travels in close contact with a coolingroll whereat said vacuum deposition takes place.
 6. A method ofproducing an electrolytic capacitor according to claim 3, wherein saidvacuum deposition is conducted in an argon atmosphere which ismaintained at a pressure of from 1.0×10⁻⁵ to 1.0×10⁻⁴ Torr.
 7. A methodof producing an electrolytic capacitor according to claim 3, whereinsaid deposition angle is gradually varied during said deposition of saidtitanium.
 8. A method of producing an electrolytic capacitor accordingto claim 3, wherein said deposition angle φ₁ is 40° or greater.
 9. Anelectrolytic capacitor, comprising a cathode foil and an anode foilwhich are wound interposing a separator and thereafter impregnated withan electrolyte, said cathode foil being produced by applying titanium toan aluminum foil substrate, said titanium being initially applied byvacuum deposition at an initial angle φ₁ to form nuclei with a roughcolumn-like structure and, thereafter applying said titanium by vacuumdeposition at a second angle φ₂, wherein φ₁ >φ₂, to continuously grow afilm having column-like structures.
 10. A method of producing anelectrolytic capacitor comprising, causing an aluminum foil substrate tocontinuously travel onto the surface of a roll, applying titanium tosaid aluminum foil substrate, said titanium being initially applied byvacuum deposition at an initial angle φ₁ to form nuclei with a roughcolumn-like structure and, thereafter applying said titanium by vacuumdeposition at a second angle φ₂, wherein φ₁ >φ₂, to continuously grow afilm having column-like structures so as to form a cathode foil, andwinding said cathode foil together with an anode foil with a separatorinterposed therebetween to form a capacitor device.